Jurassic microbial communities in hydrothermal manganese crust of the Rifian Calcareous Chain,Northern Morocco

The stratigraphic record of the Middle and Upper Jurassic in the Western Tethys is characterized by successive eustatic and tectonic events recorded as stratigraphic unconformities, which are revealed by hardgrounds, palaeokarsts, palaeosoils, and by the deposition of Fe–Mn crusts. The study of a Mn crust from the Middle-Upper Jurassic discontinuity in the Jbel Moussa Group (Rifian Cordillera), from stratigraphic, geomicrobiologic, mineralogical, and geochemical standpoints allows us to establish its hydrothermal origin. The manganese crust is composed by Ca-birnessite, cryptomelane and coronadite. Major- and trace-elements analyses of the whole crust show high contents in MnO (> 70 wt.%), a negative Ce anomaly and a positive Eu anomaly. Analysis of the microstructures under scanning electron microscopy reveals crystalline and microbial laminations, probably owing to fungal mycelium. Mineralogical and geochemical composition, together with microbial structures, suggest that this Mn crust formed as a result of venting hydrothermal fluids through synsedimentary faults. Chemosynthetic microbes were probably involved in the precipitation of Mn.     

热液矿床中萤石的稀土元素地球化学及其地质意义

萤石是许多热液矿床中重要的脉石矿物,其稀土元素含量及相关参数（如∑REE、LREE/HREE、Eu/Eu^*、Ce/Ce^*、Y/La、Tb/Ca-Tb/La图解等）,能为揭示成矿流体性质、来源与演化,建立成矿模式,评价区域成矿潜力等提供重要信息。然而,随着微区分析技术的日趋成熟,原位实测数据显示,萤石中微量元素（包括稀土元素）的分配在显微尺度上可能具有不均一性,致使依据萤石溶液法获得的稀土元素含量所反映地质信息的可靠性受到质疑。因此,在应用萤石稀土元素地球化学探讨相关地质问题前,有必要加强萤石微观结构的观察和配套的流体包裹体以及相关同位素组成分析。本文在综述萤石稀土元素地球化学研究基础上,初步探讨了影响萤石稀土元素不均一分配的主要机制,以期为萤石稀土元素在热液矿床成因研究中的应用提供借鉴。     

Late Jurassic tectonics and sedimentation: breccias in the Unken syncline,central Northern Calcareous Alps

This study analyses and discusses well preserved examples of Late Jurassic structures in the Northern Calcareous Alps, located at the Loferer Alm, about 35 km southwest of Salzburg. A detailed sedimentary and structural study of the area was carried out for a better understanding of the local Late Jurassic evolution. The Grubhörndl and Schwarzenbergklamm breccias are chaotic, coarse-grained and locally sourced breccias with mountain-sized and hotel-sized clasts, respectively. Both breccias belong to one single body of breccias, the Grubhörndl breccia representing its more proximal and the Schwarzenbergklamm breccia its more distal part, respectively. Breccia deposition occurred during the time of deposition of the Ruhpolding Radiolarite since the Schwarzenbergklamm breccia is underlain and overlain by these radiolarites. Formation of the breccias was related to a major, presumably north-south trending normal fault scarp. It was accompanied and post-dated by west-directed gravitational sliding of the Upper Triassic limestone (“Oberrhätkalk”), which was extended by about 6% on top of a glide plane in underlying marls. The breccia and slide-related structures are sealed and blanketed by Upper Jurassic and Lower Cretaceous sediments. The normal fault scarp, along which the breccia formed, was probably part of a pull-apart basin associated with strike slip movements. On a regional scale, however, we consider this Late Jurassic strike-slip activity in the western part of the Northern Calcareous Alps to be synchronous with gravitational emplacement of “exotic” slides and breccias (Hallstatt mélange), triggered by Late Jurassic shortening in the eastern part of the Northern Calcareous Alps. Hence, two competing processes affected one and the same continental margin.     

Evidence for Jurassic subduction from the Northern Calcareous Alps (Berchtesgaden; Austroalpine,Germany)

The closure of the western part of the Neotethys Ocean started in late Early Jurassic. The Middle to early Late Jurassic contraction is documented in the Berchtesgaden Alps by the migration of trench-like basins formed in front of a propagating thrust belt. Due to ophiolite obduction these basins propagated from the outer shelf area (=Hallstatt realm) to the interior continent (=Hauptdolomit/Dachstein platform realm). The basins were separated by nappe fronts forming structural highs. This scenario mirrors syn-orogenic erosion and deposition in an evolving thrust belt. Active basin formation and nappe thrusting ended around the Oxfordian/Kimmeridgian boundary, followed by the onset of carbonate platforms on structural highs. Starved basins remained between the platforms. Rapid deepening around the Early/Late Tithonian boundary was induced by extension due to mountain uplift and resulted in the reconfiguration of the platforms and basins. Erosion of the uplifted nappe stack including obducted ophiolites resulted in increased sediment supply into the basins and final drowning and demise of the platforms in the Berriasian. The remaining Early Cretaceous foreland basins were filled up by sediments including siliciclastics. The described Jurassic to Early Cretaceous history of the Northern Calcareous Alps accords with the history of the Western Carpathians, the Dinarides, and the Albanides, where (1) age dating of the metamorphic soles prove late Early to Middle Jurassic inneroceanic thrusting followed by late Middle to early Late Jurassic ophiolite obduction, (2) Kimmeridgian to Tithonian shallow-water platforms formed on top of the obducted ophiolites, and (3) latest Jurassic to Early Cretaceous sediments show postorogenic character.     

Rare earth elements in high-grade metamorphic rocks from the western Alps

A sequence of amphibolite to granulite facies metasedimentary and mafic metaigneous rocks from the western Italian Alps has been analysed for rare earth elements (REE). In this sequence, the metasedimentary granulites have probably been affected by a melting event while the metaigneous granulites remained unaffected. Metasedimentary granulites have a less fractionated chondrite-normalized REE pattern than equivalent amphibolite facies rocks. The granulites tend to have a higher content of heavy REE and lower abundances of light REE (LREE). The leucosomes of migmatitic granulites have lower REE content than the melanocratic bands and both these rock types have variable relative abundances of Eu. The mafic granulites have LREE enriched patterns while the amphibolites are slightly depleted in LREE. The differences between the mafic granulites and amphibolites are probably of pre-metamorphic origin.     

Zoned calcites in Jurassic ammonite chambers: trace elements, isotopes and neomorphic origin

Zoned calcites were found in the phragmacone chambers of three Sonniniid ammonites from marine Middle Jurassic sandstones (Isle of Skye, U.K.). Each ammonite has a unique sequence of up to nine zones of calcite which fill or partially fill the chambers. Zones are defined by changes in the density of minute opaque inclusions and variation in trace-element composition. Proximal (early) calcites have undulose extinction and some exhibit the specific fabrics of fascicular-optic and radiaxial fibrous calcites. Microdolomite inclusions are found in one specimen. Early calcites, interpreted as replacements after a single isopachous fringe of acicular carbonate (probably high magnesium calcite), are succeeded by blocky ferroan calcite cement. In one specimen there are two distinct generations of calcite, in the others there is a continuous mosaic incorporating both early calcites and late cement. Isotopic composition of the early calcite zones demonstrates the initial importance of organic derived carbon (δ¹³C =— 26‰, δ¹⁸O ‰ O). Further cementation and mineralogical stabilization took place at increased temperatures and probably after modification of the pore water isotopic composition (calcites with δ¹³C =— O‰, δ¹⁸O～— 10‰). The distinctive fabrics and zonal patterns probably developed during the replacement of the precursor cement and are not primary growth features. Reversals in isotopic and trace element trends are believed to be related to the rate of neomorphic crystal growth and hence to the degree of exchange with external pore waters. Further increase in temperature, probably during Tertiary igneous activity, gave rise to the extremely light δ¹⁸O values of the late cements in the ammonite which had previously had least contact with external waters (cements with δ¹³C ～ O, δ¹⁸O ～— 20‰).     

The change from rifting to thrusting in the Northern Calcareous Alps as recorded in Jurassic sediments

Facies analysis, fossil dating, and the study of the metamorphism in the Late Triassic to Early Cretaceous sedimentary successions in the central part of the Northern Calcareous Alps allow to reconstruct the tectonic evolution in the area between the South Penninic Ocean in the northwest and the Tethys Ocean with the Hallstatt Zone in the southeast. The Triassic as well as the Early and Middle Jurassic sediments were deposited in a rifted, transtensive continental margin setting. Around the Middle/Late Jurassic boundary two trenches in front of advancing nappes formed in sequence in the central part of the Northern Calcareous Alps. The southern trench (Late Callovian to Early Oxfordian) accumulated a thick succession of gravitatively redeposited sediments derived from the sedimentary sequences of the accreted Triassic–Liassic Hallstatt Zone deposited on the outer shelf and the margin of the Late Triassic carbonate platform. During a previous stage these sediments derived from sequences deposited on the more distal shelf (Salzberg facies zone of Hallstatt unit, Meliaticum), and in a later stage from more proximal parts (Zlambach facies zone of Hallstatt unit, Late Triassic reef belt). Low temperature–high pressure metamorphism of some Hallstatt limestones before redeposition is explained by the closure of parts of the Tethys Ocean in Middle to Late Jurassic times and associated subduction. In the northern trench (Late Oxfordian to Kimmeridgian) several hundred meters of sediment accumulated including redeposited material from a nearby topographic rise. This rise is interpreted as an advancing nappe front as a result of the subduction process. The sedimentary sealing by Tithonian sediments, documented by uniform deep-water sedimentation (Oberalm Formation), gives an upper time constraint for the tectonic events. In contrast to current models, which propose an extensional regime for the central and eastern Northern Calcareous Alps in the Late Jurassic, we propose a geodynamic model with a compressional regime related to the Kimmerian orogeny.     

Rare earth elements in ‘Younger’ granites,Northern Portugal

Rare earth elements (REE) were determined in two suites of Hercynian ‘Younger’ granodiorites and granites, one massive and the other porphyritic. Within each suite, the REE abundances decrease towards the more felsic granite while the REE patterns are almost identical. The patterns of the porphyritic types are only slightly more fractionated than those of the massive rocks. Negative Eu-anomalies are observed in all rocks although those of the granodiorites are smaller than those of the granites. Modeling of the data indicates that the granitic magmas may be derived, by partial melting, from the greywackes and pelites of the orogenic belt, the melts being in equilibrium with a residuum composed of quartz, plagioclase, garnet, orthopyroxene or cordierite, and, possibly, biotite.     

Structural synthesis of the Northern Calcareous Alps, TRANSALP segment

The Northern Calcareous Alps (NCA) are the site of very large top-to-north convergent movements during Cretaceous–Tertiary Alpine mountain building. To determine the amount of shortening, the depth of detachment and the style of deformation, we retro-deformed an approximately 40 × 40 km area comprising the Lechtal and Allgäu Nappes. On the basis of all available geological data and processed sections of the TRANSALP reflection seismic experiment, coherent 3D models were constructed by splining lines from N–S cross-sections. Integration of 3D kinematic modeling and field data shows the following. The structure of the Lechtal Nappe is controlled by the Triassic Hauptdolomit. Four main thrusts link to a detachment at 2–6 km depth below sea level. Shortening estimates vary, from 25% (east) to 42% (west). Additional contraction is accommodated by folding. In the east the subjacent Allgäu Nappe can be traced about 10 km down-plunge, and is shortened by about one third. In the western part the downplunge width is at least 15–20 km, with restorable shortening of one third. The triple (Inntal, Lechtal, Allgäu Nappes) NCA nappe system was moved uniformly N–S to produce laterally heterogeneus shortening of 40–90 km or 50–67%. We suggest that the NCA are underlain by substantial amounts of buried Molasse sediments and/or overthrust units of Helvetic and Rheno-Danubian Flysch, indicating post-Eocene N–S shortening of at least 55 km. Restored to an initial configuration, the basin topography of the NCA reveals strong E–W thickness variations of the Triassic Wettersteinkalk and Hauptdolomit platform carbonates. Such variations may pertain to N–S trending growth faults, which were important precursors to later Jurassic extension of the Austroalpine passive margin. Such structures are unlikely to be seen in the conventional N–S cross-sections, but form an essential geometrical and mechanical element in later, convergent mountain building.     

大厂锡—多金属矿床热液喷气沉积成因的证据——容矿岩石的微量元素及稀土元素地球化学

对大厂锡矿床容矿岩石稀土元素地球化学研究表明，本矿区主要容矿岩石——硅质岩、富长石岩及电气石岩稀土元素总量低，具弱的Ce亏损，明显的Eu负异常。这些特点与某些 有代表性矿床中的热液喷气沉积岩一条带状燧石岩及电气石岩十分相似，证明了它们属于喷气沉积成因。相反，与主要容矿岩石互成条带的部分绢云母岩，含绢云母的长石岩等则稀土总量高，轻重稀土分馏明显，与北美页岩相似，具有陆源沉积或混合成因的特征。运用聚类分析的方法，这些岩石的微量元素地球化学分类与上述结果完全一致，为其成因进一步提供了佐证。     

Carbonates in Upper Permian evaporites of the Northern Calcareous Alps,Austria

Thin black dolomites occur within the evaporitic Alpine Haselgebirge Formation (Late Permian) of the central and eastern Northern Calcareous Alps, Austria. They have been compared with the southalpine Bellerophon Formation byTollmann (1964). Samples obtained from the gypsum-anhydrite deposit of Wienern am Grundlsee, Styria, are mostly unfossiliferous mudstones (dolomicrite and dolomicrospar) devoid of sedimentary structures. Only few samples contain a low-diversity ostracode fauna. Electron microprobe and X-ray diffraction analysis indicate well-ordered and near-stoichiometric dolomite (49.9±0.2 mol% CaCO₃). The oxygen isotopic composition varies between –3.0 and –5.7 PDB. The ¹³C ratios fall into two distinct groups: –0.9 to +1.9, and –3.5 to –6.8 PDB. The carbon isotope data of the first group indicate a predominantly marine origin of the carbonates. The significantly depleted ¹³C ratios of the second group are probably due to freshwater influx into the basin and/or sulfate reduction. Sulfur and strontium isotope data from intercalated anhydrite and gypsum preclude an entirely non-marine origin of the brines. The light ¹⁸O ratios are probably due to early diagenetic sulfate reduction and/or dolomite recrystallization during moderate burial. A detailed interpretation of the depositional environment is rendered impossible because of the pervasive alpine tectonics. However, northalpine Bellerophon carbonates appear to be restricted to areas of major anhydrite deposition, and are absent in the halitedominated facies.

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Zusammenfassung Im zentralen und östlichen Abschnitt der Nördlichen Kalkalpen Österreichs treten geringmächtige, bituminöse Dolomite im Verband der salinaren Alpinen Haselgebirge Formation (Oberperm) auf. Sie wurden vonTollmann (1964) mit der südalpinen Bellerophon Formation verglichen. Bei den untersuchten Proben von der Gips- und Anhydritlagerstätte Wienern am Grundlsee (Steiermark) handelt es sich fast durchwegs um fossilleere Mikrite und Mikrosparite, die keinerlei Sedimentstrukturen aufweisen. Nur sehr wenige Proben führen Ostrakoden. Nach Mikrosonden-Analysen und röntgendiffraktometrischen Untersuchungen bestehen diese mikrokristallinen Dolomite aus fast stöchiometrischen, gut geordneten Dolomit (49.9±0.2 Mol% CaCO₃). Die Sauerstoffisotopenwerte schwanken von –3.0 bis –5.7 PDB und die ¹³C Verhältnisse fallen in zwei Gruppen: –0.9 bis +1.9, und –3.5 bis –6.8 PDB. Die Werte der ersten Gruppe indizieren eine im wesentlichen marine Bildung der Karbonate. Die deutlich leichteren ¹³C-Werte der zweiten Gruppe können durch Süßwassereinfluß während der Sedimentation und/oder durch Sulfatreduktion erklärt werden. Schwefel- und Strontium-Isotopenwerte, gemessen an Anhydriten und Gipsen im Verband mit den Dolomiten, schließen eine rein nicht-marine Herkunft der Salzlösungen aus. Die negativen ¹⁸O-Verhältnisse der Dolomite sind wahrscheinlich auf diagenetische Prozesse (Sulfatreduktion und/oder Umkristallisation) zurückzuführen. Die enorme alpidische Deformation dieser Evaporitserien gestattet es nicht, das ursprüngliche Ablagerungsmilieu der Karbonate zu rekonstruieren. Die nordalpinen Bellerophon Karbonate scheinen jedoch an Ablagerungsbereiche mit mächtiger Anhydritbildung gebunden zu sein, und fehlen primär in der Halit-dominierten Fazies.

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Résumé En Autriche, dans les secteurs central et oriental des Alpes calcaires du nord, existent des dolomies bitumineuses de faible puissance en relation avec la formation évaporitique alpine de l'Haselgebirge (Permien supérieur).Tollmann (1964) les a comparées à la formation sud-alpine de Bellérophon. Des échantillons provenant des gisements de gypse et d'anhydrite de Wienern sur le Grundlsee (Styrie) montrent des mudstones (dolomicrites à dolomicrosparites) dépourvus de fossiles et de structures sédimentaires. Seuls quelques échantillons contiennent une faune à ostracodes peu diversifiée. Les examens à la microsonde et aux rayons X montrent une dolomite bien ordonnée et quasi-stoechiométrique (49,9±0,2% moléculaire de CaCo₃). La composition isotopique de l'oxygène varie entre –3,0 et –5,7 PDB. Les rapports ¹³C se répartissent en deux groupes: –0,9 à +1,9 et –3,5 à –6,8 PDB. Ces données indiquent pour le premier groupe une origine surtout marine des carbonates. Les valeurs moins élevées des rapports du second groupe sont dues probablement à l'arrivée d'eau douce dans le bassin et/ou à une réduction des sulfates. Les valeurs isotopiques du soufre et du strontium, mesurées sur les gypses et anhydrites associés aux dolomies, excluent une origine entièrement continentale pour les saumures. Les faibles rapports ¹⁸O sont dûs probablement à une réduction diagénétique précoce des sulfates et/ou à la recristallisation de la dolomite pendant l'enfouissement. Une interprétation détaillée des conditions de dépôt est rendue impossible par l'ampleur de la déformation tectonique alpine. Il semble toutefois que des carbonates nord-alpins de type «Bellérophon» soient liés aux aires de forte sédimentation d'anhydrite et soient absents dans les faciès à halite dominante.

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Haselgebirge ( ) . Tollmann (1964) . , Grundlsee, , , - . . - , - , (49.9–0,2 % ₃). –3,0 –5,7% PDB, ¹³C : –0,9 –1,9% –3,5 –6,8% PDB. . / . , , , . ¹⁸ , , : / . . , , » « .

     

Mid-Cretaceous,primitive alkaline magmatism in the Northern Calcareous Alps: Significance for Austroalpine Geodynamics

Basanitic dykes (local name: Ehrwaldite) occur over a distance of at least fifty kilometres in a narrow, east-west trending zone within the Lechtal nappe of the Northern Calcareous Alps. The dykes crosscut Mesozoic sedimentary strata up to the Lower Cretaceous. The sedimentary rocks show contact-metamorphism in the immediate vicinity of the dykes. The Ehrwaldites vary in mineral content from olivine (fo 91–87) — titanian augite basanites to basanites containing also kaersutite, titanian biotite and zeolites. Minor phases are titanian magnetite, picotite, llmenite, carbonate and Sulfides. Mantle derived xenoliths and xenocrysts form up to five percent of the rock. Bulk chemical analyses show the typical characteristics of nepheline basanites (ne = 11–17 wt%; mg-number = 74–78) and demonstrate that the Ehrwaldites are primitive mantle-derived melts. Trace element contents of the dykes are in excellent agreement with those for basanites and olivine-nephelinites from Tertiary and Quaternary European Provinces. The same is true for the isotope characteristics of the dykes with average initial _Sr and _Nd values of –8.2 and +4.7, respectively. These data demonstrate similarities in the mantle source rocks and in the melting characteristics with European alkaline rocks and thus similarities in the European subcontinental mantle at different localities for the last 100 Ma. These data are in clear contrast with the value for the penninic suboceanic mantle. Geochemical constraints and piston cylinder experiments indicate a depth of origin of > 80 kilometres at temperatures of at least 1250 °C for the Ehrwaldites. Potassium-argon bulk rock data of petrographically different samples of the dykes from different localities yield consistent ages around 100 Ma (Upper Albian). After emplacement, the Ehrwaldites underwent conditions of the »zone of diagenesis« with temperatures around 120 °C which the late magmatic zeolites survived.For the evolution of the Northern Calcareous Alps west of Innsbruck this means that there was no subduction zone beneath the Northern Calcareous Alps at the time of magma ascent. The dykes intruded in an extensional regime when the Northern Calcareous Alps had not yet suffered thrust faulting. The Northern Calcareous Alps were still part of a continental basement far away from a possible Penninic subduction zone. To account for the ascent of the basanitic Ehrwaldite melts, a horst-graben system is proposed, possibly related to transpressive tectonics.

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Zusammenfassung Basanitische Ganggesteine (Lokalbezeichnung Ehrwaldite) treten in einer schmalen, über fünfzig Kilometer langen, Ost-West verlaufenden Zone der Lechtal-Decke in den Nördlichen Kalkalpen auf. Die Ganggesteine durchschlagen mesozoische Sedimente bis zur Unterkreide, welche in unmittelbarer Umgebung der Gänge kontakt-metamorphisiert wurden. Die basanitischen Gesteine enthalten neben zum Teil noch frischem Olivin (fo 91–87) wechselnde Anteile von Titanaugit, Kaersutit, Titanbiotit und Zeolithen. Nebengemengteile sind Titanomagnetit, Picotit, Apatit, Ilmenit, Karbonat und Sulfide. Mantelxenolithe und Mantelxenokristalle können bis zu fünf Prozent des Gesteins ausmachen. Die Gesamtgesteinschemie der Ehrwaldite belegt deren Charakter als primitive Mantelschmelzen und ist typisch für Nephehnbasanite (ne = 11–17 Gew.%, mg-Zahl = 74–78). Alle Spurenelementgehalte der Ehrwaldite stimmen ausgezeichnet mit denjenigen von Basaniten und Olivinnepheliniten tertiärer und quartärer Vulkanprovinzen in Europa überein. Dasselbe gilt für die Isotopencharakteristik der Gänge (mittleres _Nd von + 4.7, mittleres _Sr von –8.2). Die Daten belegen ähnliche Mantelausgangsgesteine und Schmelzcharakteristika wie für andere europäische Alkaligesteine und damit Ähnlichkeiten des europäischen subkontinentalen Mantels an verschiedenen Orten für den Zeitraum der letzten 100 Millionen Jahre. Die Isotopendaten stehen im eindeutigen Gegensatz zur Isotopencharakteristik des penninischen subozeanischen Mantels. Geochemische Daten und laufende Piston Cylinder Experimente ergeben eine Ursprungstiefe der Ehrwaldite als Mantelteilschmelzen von > 80 km bei Temperaturen von mindestens 1250 °C. K-Ar Gesamtgesteinsalter der Ehrwaldite an petrographisch verschiedenen Proben aus verschiedenen Aufschlüssen ergeben sehr konsistente Alter von ca. 100 Millionen Jahren (oberes Alb). Nach ihrer Platznahme erlitten die Ehrwaldite Bedingungen der »Diagenesezone« mit Temperaturen um 120 °C, wobei die primär gebildeten Zeohthe überlebten.Für die Entwicklung des Ostalpins westlich von Innsbruck bedeutet dies, daß zur Zeit des Magmenaufstiegs keine Subduktionszone unter den Nördlichen Kalkalpen bestand. Dieser Magmenaufstieg erfolgte in einem Gebiet mit Extension, als die Nördlichen Kalkalpen noch keinen Deckenbau aufwiesen und auf einem kontinentalen Sockel lagen, weit entfernt von einer penninischen Subduktionszone. Der Aufstieg der basanitischen Ehrwalditschmelzen könnte in einem Horst-Graben System erfolgt sein, welches möglicherweise Beziehungen zu transpressiver Tektonik aufwies.

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Résumé Des filons basanitiques (ehrwaldites) sont présent dans la nappe du Lechtal (Nördliche Kalkalpen) le long d'une étroite zone qui s'étend d'est en ouest sur plus de 50 Km. Ces filons traversent, jusqu'au Crétacé inférieur, les sédiments mésozoïques, qui sont légèrement métamorphisés à leur contact. Ces roches basanitiques contiennent, outre de l'olivine relativement fraîche (fo 91–87), de l'augite, de la biotite titanifère, de la kaersutite et des zéolites en quantités variables. Les minéraux accessoires identifiés sont la titano-magnétite, la picotite, l'apatite, l'ilménite, des carbonates et des sulfures. Des xénolithes et des xénocristaux provenant du manteau peuvent représenter jusqu'à 5% de la roche. La composition chimique des ehrwaldites, caractéristique de basanites à néphéline, montre qu'elles représentent un liquide primitif de fusion mantellique. Les teneurs en éléments en trace de ces roches correspondent parfaitement à ceux de basanites et de néphélinites à olivine que l'on trouve dans différentes provinces volcaniques européennes tertiaires et quaternaires. De telles analogies ont également été mises en évidence en ce qui concerne les caractéristiques isotopiques des filons qui montrent des valeurs initiales moyennes de ESr = –8.2 et ENd = +4.7. Ces données démontrent qu'entre les roches ici en question et les roches alcalines de diverses régions d'Europe, il existe une similitude quant aux roches parentales mantelliques et au processus de fusion et qu'il existe donc une similitude dans la nature du manteau subcontinental européen pendant les 100 derniers Ma. Ces données se distinguent nettement de celles qui caractérisent le manteau subocéanique du domaine pennique. Des données géochimiques complémentaires et des expérimentations de type cylindre/piston actuellement en cours indiquent pour les ehrwaldites une profondeur d'origine supérieure à 80 Km et des températures d'au moins 1250 °C. Les analyses géochronologiques K-Ar réalisées sur des échantillons provenant de différentes localités et de compositions pétrographiques diverses donnent des âges très comparables de 100 Ma. Après leur mise en place, les ehrwaldites ont subi des conditions typiques de la zone de diagenèse (T 120 °C), dans lesquelles les zéolites primaires ont été préservées.On peut déduire de ces résultats diverses conséquences sur le développement du domaine austroalpin à l'ouest d'Innsbruckr il n'existait pas de zône de subduction sous des Nördliche Kalkalpen pendant l'ascension des magmas; cette ascension a eu lieu au cours d'une phase d'extension, durant laquelle les Nördliche Kalkalpen n'avaient pas encore fait l'objet de phénomènes de charriage et participaient à un socle continental très éloigné de la zone de subduction pennique. L'ascension de ces ehrwaldites a pu avoir lieu le long d'un système en horst et graben, en relation avec une tectonique transformante.

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- « » (Ehrwaldite) 50 . , . (fo 91–87) , , . , , , , . 5 % . (ne - 11–17 .-%, mg-zahl - 74–78 ). . : _nd+4,7 _Sr-8,2. , , .. 100 . , . , , 80 , no- , 1250°. , - , , 100 , .. . 120°, . , . , . - , , transpressiver Tektonik.

     

Authigenic aluminium phosphate-sulphates in sandstones of the Mitterberg Formation, Northern Calcareous Alps, Austria

Complex aluminium phosphate-sulphate minerals of the hinsdalite group have been identified as early diagenetic precipitates in Late Permian sandstones of the Northern Calcareous Alps, western Austria. According to their chemical composition they can be regarded as solid solutions between woodhouseite, svanbergite, crandallite and goyazite. The model proposed for their origin involves the dissolution of detrital apatite in a low-pH environment and subsequent precipitation of aluminium phosphate-sulphate minerals, which clearly pre-date syntaxial quartz cementation of the sediment. Their occurrence probably has been overlooked in other sandstones showing diagenetic apatite dissolution. The recognition of such minerals could provide a significant insight into early phosphate diagenesis.     

Growing folds and sedimentation of the Gosau Group, Muttekopf, Northern Calcareous Alps, Austria

Analysis of the three-dimensional geometry of Upper Cretaceous clastics in the Muttekopf area (Northern Calcareous Alps, Austria) indicate fold and fault structures active during deposition. Coniacian continental to neritic sedimentation (Lower Gosau Subgroup) was contemporaneous with displacements on NW-trending faults and minor folding along NE-trending axes. From the Santonian onwards (sedimentation of the deep-marine Upper Gosau Subgroup) the NW-trending faults were sealed and large folds with WSW-trending axes developed. The direction of contraction changed to N-S after the end of Gosau deposition in the Danian (Paleocene). Synorogenic sedimentation patterns indicate continuous contraction from the Coniacian to the Late Maastrichtian/?Danian. Therefore, large-scale extension as observed in the central part of the Eastern Alps cannot be documented in the western parts of the Northern Calcareous Alps. A combination of subduction tectonic erosion for the frontal parts and gravitational adjustment of an unstable orogen after nappe stacking for the internal parts possibly accounts for the different development of Gosau basins in the frontal and trailing regions of the Austroalpine wedge.     

Pyritic shales and microbial mats: Significant factors in the genesis of stratiform Pb-Zn deposits of the Proterozoic?

Extensive horizons of pyritic shale occur in Mid-Proterozoic sediments of the eastern Belt basin, Montana, U.S.A. These pyritic shales are of striped appearance. Laminated pyrite beds alternate with nonpyritic shale beds. Laminated pyrite beds have wavycrinkly internal laminae and are interpreted as mineralized microbial mats. Pyrite is essentially the only sulfide mineral in these shales. Pyritic shale horizons occur along the basin margins, and it is feasible that colloidal iron was introduced by rivers into basin marginal lagoons and then incorporated into microbial mats and reduced to pyrite. The pyritic shales in the Newland Formation show great similarity to those that host the Pb-Zn deposits of Mt. Isa and McArthur River. It is suggested that pyritic shales of this kind are relatively common in Mid-Proterozoic shales, and that the processes that led to the occasional formation of Pb-Zn ore bodies in these shales are not related to those that formed the pyritic shales themselves.     

The genesis of Lofer cycles of the Dachstein Limestone,Northern Calcareous Alps,Austria

Peritidal carbonate platform Lofer cycles have been regarded as a record of sea-level oscillations driven by variations in the earth's orbit. Fresh analysis of a newly measured 700 m thick section from the Steinernes Meer is presented here. Estimation of stratigraphic completeness indicates that this sequence is only 0.75–9.5% complete, strongly suggesting that Milankovitch patterns are not preserved. Analysis of cycle thickness-frequency distributions reveals an exponential pattern, strongly suggestive of aperiodic, random deposition rather than periodic deposition in response to orbital forcing. Evidence for the importance of autocyclic processes (e.g. lateral migration of inter- to supratidal mudbanks and subtidal areas) and syn-sedimentary tectonic downfaulting events within this already active Late Triassic extensional zone is presented.     

Fertiliser characterisation: Major,trace and rare earth elements

In recent years, there has been increasing concern regarding the chemical impact of agricultural activities on the environment so it is necessary to identify contaminants, and/or characterise the sources of contamination. In this study, a comprehensive chemical characterisation of 27 fertilisers of different types used in Spain has been conducted; major, minor and trace elements were determined, including rare earth elements. Results show that compound fertilisers used for fertigation or foliar application have low content of heavy metals, whereas fertilisers used for basal and top dressing have the highest content of both REE and other heavy metals. REE patterns of fertilisers have been determined in order for them to be used as tracers of fertilisers in future environmental studies. Furthermore in this work REE patterns of fertilisers are used as tracers of the source of phosphate in compound fertilisers, distinguishing between phosphorite and carbonatite derived fertilisers. Fertilisers from carbonatites have higher contents of REE, Sr, Ba and Th whereas fertilisers from phosphorites have higher contents of metals of environmental concern, such as Cd, U and As; and the sum of the heavy metals is higher. Some of the analysed fertilisers have Cd concentrations that exceed maximum values established in some countries and can be expected to produce long-term soil accumulation. Furthermore, other elements such as U, As and Cr are 10–50 times higher in concentration than those of Cd, but there is no legislation regarding them, therefore it is necessary to regulate fertiliser compositions in order to achieve environmental protection of soils and waters.     

Mineralogy and geochemical behavior of trace elements of hydrothermal alteration types in the volcanogenic massive sulfide deposits,NE Turkey

Volcanogenic massive sulfide (VMS) deposits of the Eastern Pontides, Turkey, are hosted by the Maastrichtian–Eocene dacite and rhyodacite series, accompanied by lesser andesite and basalts, as well as their pyroclastic equivalents, with tholeiitic to calc-alkaline affinity. The ore mineral assemblages are chalcopyrite, sphalerite, galena, chalcocite, covellite, bornite, and tetrahedrite. Potassic-, phyllitic- (sericitic), argillic- (kaolinitic and smectitic), silicic-, propylitic- and hematitic-alteration is commonly associated with these deposits.HFSE, LILE, TRTE and REE contents show strong variability in different alteration types resulting from interaction with acid or alkaline fluids. Sample groups showed chondrite-normalized enrichment of LREE relative to HREE and sub-parallel trends, except for the hematitic- and phyllitic-alteration types. MREE are strongly depleted in the zones of most intense silicification and kaolinization. Most sample groups have strongly- to slightly-negative Eu anomalies, ranging from 0.35 to 0.88 (mean); hematitic- (1.45) and propylitic-altered rocks (1.11) have slightly- to moderately-positive anomalies. The negative Eu anomalies indicate the low temperatures of fluids (< 200 °C). In contrast, the positive Eu anomalies result from high-temperature hydrothermal conditions (> 200 °C). No Ce anomaly was observed, except for phyllitic alteration where a slight positive anomaly was noted. The chondrite-normalized trace and REE patterns of the altered rocks are similar to each other, suggesting that they were derived from a common felsic source. The alteration groups formed from acid, intermediate, and alkaline hydrothermal solutions. Some transition, base and precious metals and volatile elements were clearly enriched, especially in the hematitic-, silicic-, kaolinitic- and phyllitic-altered samples. The other elements exhibit different behaviors in different sample groups. REE behavior is relatively immobile in the silicic-, hematitic-, kaolinitic- and partially in moderately- and propylitic-altered rocks, based on mass-balance calculations. LILE and HFSE appear mobile in the altered sample groups, except in the propylitic-altered rocks. TRTE behave as relatively immobile in most of samples, except in some of the silicic- and phyllitic-altered rocks, and especially in the hematitic-altered samples. HFSE, most of the transition (W, Mo, Cu, and Sb) and some other trace elements (Pb, As, Hg, Bi, Se and Tl), are enriched in the hematitic-altered samples and in the some silicic-altered samples. The highest As, Bi, Mo, Se and Hg concentrations in the hematite-altered samples can be used to distinguish other alteration types and may be a useful indicator in a prospect-scale base metal exploration.